Catheters have been utilized in the medical industry for many years. One of the greatest challenges in using a catheter is controlling the position and placement of the catheter tip from a remote location outside of the patient's body. Some catheters have features designed to aid in steering the catheter and overcoming this challenge.
However, several significant problems are still encountered with these catheters. The devices typically have pre-formed inner catheters which are placed in an outer guiding sheath. When the inner catheter is extended or the sheath withdrawn, the inner catheter assumes a different shape. It is usually necessary to draw the inner catheter back into the outer guiding sheath to reshape the catheter tip, and then extend the inner catheter out of the outer sheath for each successive use in another location.
Steerable catheters generally have closed, solid or substantially solid central areas rather than hollow central lumens because of the tendency of lumened steerable catheters to collapse. Since the lumen region is solid, it is not possible to pass another structure, such as a laser catheter, through the steerable catheter.
Steerable catheters exhibit different properties when positioned in a patient's body rather than outside the body. After insertion into the body, the material of the steerable catheter is warmed, and the catheter may absorb water. As a result, the steerable catheter may not perform as desired because of the change in the plastic characteristics.
Also, known steerable catheter distal tips exhibit non-fluid movements. The catheter distal tip often bends with only exaggerated and imprecise movements. A locking cam must be tightened or the handle held in place once the tip is in place during the medical procedure, which also contributes to imprecise movements of the tip. These devices also lack the ability to make very small movements, such as fight radius turns. Also, wire controlled steerable catheters may experience undesired wire deformation over time which affects control.
Torque has also been a significant disadvantage encountered with known steerable catheters. As the steerable catheter travels through the body, different drag forces are created on the catheter. A loss in torque results, and additional power to make the catheter proceed through the body is required.
Another type of steerable catheter uses a bellows which aids in catheter bending. The bellows stretches and collapses as the catheter is moved. However, in steerable catheters having a bellows configuration, the inner surface of a central lumen of the catheter is often configured so that passage of any structure through the central lumen, such as a laser catheter, is impaired.